Truing mechanism



1954 F. s. HAAS ETAL TRUING MECHANISM 3 Sheets-Sheet 1 Filed Feb. 10, 1951 illikwz wwm my M W Q m; W a A 2M MW f Q 7 l W; C

Patented Jan. 12, 1954 TRUING MECHANISM Frederick S. Haas, Orgonia, and Winthrop Trible, Cincinnati, Ohio, assignors to The Cincinnati Milling Machine 00., Cincinnati, Ohio a corporation of Ohio Application February 10, 1951, Serial No. 210,302

Claims. 1

This invention relates to grinding machines and more particularly to improvements in mechanism for truing the grinding wheels thereof. In order to grind surfaces of different shapes in a grinding machine, it is necessary to utilize a grinding wheel having a profile corresponding to the desired shape. In such cases, it is economical to provide a grinding wheel for each shape to be ground, and sometimes even separate machines are provided so that a type of truing mechanism suitable for producing the shape may be permanently mounted on the machine. Otherwise, if different shapes are to be ground on the same machine, it is necessary to change both the wheel and the truing mechanism which means longer set-up time to get them both in the same relation that they had previously. By means of this invention two truing mechanisms are permanently mounted on one machine in such relation as not to interefere with one another but on the other hand so that they will cooperate with their respective wheels when mounted in the usual manner on the wheel supporting spindle.

It is thus an object of this invention, to provide in a grinding machine, two difierent types of truing mechanism in operative relation to a common grinding wheel spindle for selective utilization of either truing mechanism dependent upon the wheel in situ.

Another object of this invention is to provide a common control mechanism for more than one truing mechanism which will control the power operation of either mechanism and effect automatically the necessary adjustments of the various supports to compensate for each reduction in wheel size effected by a truing cycle regardless of which mechanism is being utilized.

It is a further object of this invention to provide a grinding machine with truing mechanisms, so that wheels of diflerent profiles may be readily interchanged on the machine spindle but still each will be in proper working relation to its respective truing mechanism.

Other objects and advantages of the present invention should be readily apparent by reference to the following specification, considered in conjunction with the accompanying drawings forming a part thereof, and it is to be understood that any modifications may be made in the exact structural details there shown and described, within the scope of the appended claims, without departing from or exceeding the spirit of the invention.

Referring to the drawings in which like numerals indicate like or similar parts:

Figure 1 is a side elevation partly in section showing the mounting and relationship of two truing devices with respect to the grinding wheel spindle.

Figure 2 is an enlarged section on the line 2-2 of Figure 1.

Figure 3 is an enlarged section on the line 3-3 of Figure 1, looking up from the bottom.

Figure 4 is an enlarged section on the line 4-4 of Figure 1.

Figure 5 is a detail section on the line 5-5 of Figure 4.

Figure 6 is a vertical section on the line 6-6 of Figure 1.

Figure 7 is a diagram of the hydraulic control circuit.

Figure 8 is a detail view of the work slide feeding mechanism.

Figure 9 is a diagram of the electrical control circuit.

Figure 10 is a digrammatic view showing the cyclic movements of the truing diamonds and the trip control limit switches.

The adaptation of this invention has been illustrated in connection with a grinding machine of the type shown in United States Letters Patent 2,478,562. In Figure 1 of the drawings, the reference numeral lll indicates a grinding wheel of such a machine mounted on a grinding wheel supporting spindle H which is suitably journaled in the oscillatable head I2 for movement of the grinding wheel into and out of contact with a work piece which has been indicated by the circle Hi. It is to be understood that the work piece is suitably supported for rotation on a work supporting slide as shown in said patent, and for the purposes of this disclosure a portion only of the slide is shown in Figures 1 and 8 and indicated by the reference numeral M. It is to be understood that the oscillatable head l2 swings about a pivot l 5, and this pivot is mounted on a fixed part l5 of the bed of the machine. Similarly, the slide as shown in Figure 8, is slidably supported on a fixed part 16 of the machine bed. Thus, the slide I 4 is capable of relative longitudinal movement with respect to the oscillatable head I2, and in so doing would move the work piece I3 toward and from the grinding wheel.

Since the grinding wheel is fixed with respect to the bed except for this oscillating movement it is obvious that each reduction in wheel size effected by a truing operation necessitates readjustment of the parts in that the work support must be advanced toward the grinding wheel by an amount necessary to compensate diamond is not in use.

for the truing operation. Another consequence of the wheel being practically flexed is that each time a truing diamond takes a cut off of the wheel, the diamond must be advanced a similar amount to compensate for the reduction in wheel size. These adjusting movements are practically equal, and means have been provided for effecting both compensations at the same time.

One of the truing diamonds is indicated in Figure 1 by the reference numeral [1, and a second truing diamond is indicated by the reference numeral l8. The diamond I! is mounted or supported on the top of the housing [2 for traverse movement, and thus is capable of truing a straight surface on the periphery of a grinding wheel, while the diamond I8 is supported in circumferentially"spaced relation from diamond I! for swinging movement for truing curved or arcuate surfaces on the periphery of a wheel.

This arrangement makes it possible to mount a first grinding wheel on the spindle and true it with a straight face by means of diamond H, or mount a second grinding wheel on the spindle 'and true it to a curved surface by the diamond l8. Either wheel may then be remounted on the spindle, and it will be in substantially the same position. relative to its truing diamond as it had in the first instance.

Each diamond is arranged to execute a cycle position is also the rest position as when the In order that the diamonds do not interfere with wheel mounting or removal, they both have a rest position, as shown in Figure 10, on the side of the wheel next to the housing l8! for the spindle. Thus, the wheels may be pulled off the free end of the spindle without interference or damage to either diamond.

The mechanism for supporting the truing diamond I8 is shown in Figures 1 and 6. As shown in Figure 1, the diamond I8 is supported on a swinging arm 19 which is keyed to the tapered ends 20 of short shafts 2| which are journaled for rotation in the bifurcations 22 of the housing 23. The. diamond is located eccen 'tric to the axis of rotation of the shafts 2|, and

the radius may be adjusted, in fact, it may be adjusted to either side of the axis, depending upon whether it is desired to produce a concave or convex surfaceon the periphery of the wheel.

The housing 23 is, in turn, adjustably mounted on a slide 24. As shown in Figure 6, the slide 24 moves in a dovetailed guideway 25 formed in a fixed part of the housing 12. The housing 23 is pivotally mounted or supported for adjustment on a pair of tapered pivot pins 25 which are threaded in the housing 23 and engage tapered sockets 26 formed on opposite sides of the slide 24. An adjustable set screw 21 is threaded in the end of the arm 28 of the housing 23 whereby adjustment of the screw towards the slide 24 will cause the housing to swing about the pivots 25'. The extent of this movement is limited by a stop nut 29 threaded on the end of a screw 30 which is anchored in the slide 24 and passes through a slot 3| in the arm 28. Adjustment in the other direction is efiected by backing on the screw 21 and tightening up on the nut 29. This adjustment permits centering of the axis of rotation of the shafts 2| relative to the center of the face of the grinding wheel.

t In some cases it is desirable that this axis pass through the center of the wheel where the contour on each half of the wheel is the same, whereas in other cases it may be desirable to move the axis off center.

The slide 2:! makes it possible to adjust the diamond toward the wheel as the wheel wears away, and this is accomplished by a feed screw 32 which is threaded in a nut 33 forming part of the slide 24. The feed screw is journaled in a housing 34 attached to the rear end of the oscillatable wheel housing i2 and has keyed to it one member 35 of a magnetic clutch. The other member 36 is mounted for free rotation about the axis of the feed screw and is provided with an operating arm 31 as shown in Figure 4. When the magnetic clutch is electrically energized,'rotation of the member 35 imparts ro tation to the member 35 and thereby to the screw 32.

The arm 31 is connected by a link 38 to an electric solenoid 39. The arm 31 is sufficiently long to overlie the end of a spring pressed plunger 40.

The plunger 40 acts first as part of a dashpot to prevent hammering of the parts upon actuation of the solenoid and also serves as means to return the arm 31 to its original position indicated by the dotted lines 4! in Figure 4 for the next indexing stroke to effect incremental feeding movementof the diamond. In other words, the clutch is electrically energized to magnetically couple the parts 35 and 38 for joint rotation, and the solenoid is then energized to effect the rotation, the plunger acting as a dashratcheting movement.

A hand wheel .5 is attached directly to the end of the screw shaft 32 so that the the screw .may be manually actuated at will by the operator.

Similar devices have been provided for feeding the diamond H, and also for feeding the work supporting table It. For instance, in Figure 1, a housing 34 contains a magnetically operable clutch for actuating the feed screw contained in the housing 16 for moving the plunger 4% which carries the diamond il The housing 46 is mounted on a cross slide 47' mounted in a dovetailed guideway 48 and connected by a piston rod it to an actuating cylinder 58. As shown in Figure 8, another housing 35," contains a magnetic clutch for actuating the feed screw 51 which is carried by the work slide H5, and threaded in a fixed nut 52 carried by the bed of the machine, whereby rotation of the screw will adjust the work toward the wheel. Thus, all three devices may be incrementally fed by means of magnetically operated clutches and their actuating solenoids.

The diamond carrier I9 is oscillated by means of the mechanism shown in Figure 2. In this figure, the shaft 2! has a pulley 53 secured thereto, and a flexible band 54 is wrapped around the pulley and connected thereto by a pin 55 to prevent slippage between the band and the pulley.

The opposite ends of the band are connected to separate piston rods 56 and 51, which, in turn, have pistons 58 and 59 connected to the ends thereof and slidable respectively in, cylinders 50 and GI. The cylinders are formed in the housing 23.

The lower pivot shaft for the diamond carrier l9, as shown more particularly in Figure 3, is provided with a trip arm 62 which alternately engage plungers 63 and 64 for actuating control limit switches. Since the view of Figure 3 is taken looking up from the bottom of the device, it is desired to point out that the trip arm 62 will normally be in engagement with the plunger 63 when the device is at rest. A hydraulic control circuit has been provided for controlling operation of the various pistons and is shown in Figure '7. In this circuit there is a selector valve 65 and a reversing valve 66. The reversing valve is supplied with pressure fluid by a conventional pump 81 suitably located in the machine having an intake 68 for withdrawing oil from a reservoir 69 and pumping it through channel ill to pressure port ll of the reversing valve. The channel may have a suitable relief valve 12 connected thereto. The reversing valve has a valve plunger 13 in which is formed a pair of annular grooves 14 and for alternately connecting the pressure port H to motor ports 18 and 11.

These motor ports are connected by channels I8 and T9 to ports 80 and 81 respectively of the selector valve 65 which determines which hydraulic truing device will be operated. As shown in Figure '7, the valve plunger 82 of the selector valve is in a position to connect the ports 88 and 8| to ports 82 and 83 which are permanently connected to cylinders 6i and El] by channels 8:1 and 85.

It will be noted that these channels 84 and 85 are connected to the same end of cylinders 60 and BI with the result that when pressure is admitted to channel 84 the piston 59 will rotate the pulley 53 in a counterclockwise direction, and when pressure is admitted to channel 85 the pulley 53 will be rotated in a clockwise direction.

The valve plunger 82 of the selector valve may be shifted to the left by the operating knob 86, and the valve plunger will then connect ports 85 and BI to ports 81 and 88 respectively whereby the motor channels 18 and 19 will then be connected to opposite ends of cylinder 50. This cylinder contains a piston 89 which is connected to the piston rod 49 for shifting the slide 41' carrying the truing diamond I1.

The reversing valve plunger 73 is automatically shifted to the left by an operating solenoid and the plunger is drilled to receive a spring 98 which engages the end of a plunger 9| that is held against movement by a cross pin 92 mounted in the valve housing so that when the plunger 13 is moved to the left it will compress the spring against the fixed plunger 9| whereby when the operating solenoid is deenergized the spring 90 will act to return the valve plunger to the position shown. The valve plunger 13 may also be moved at will by an operating knob 93 operatively connected to the end of the plunger.

it will thus be seen that the same hydraulic actuating circuit may be used for effecting either truing cycle, the operator making the selection by proper positioning of the selector valve 55.

An electrical control circuit, Figure 9, is provided in conjunction with the hydraulic circuit to provide the necessary control means whereby either cycle may be effected automatically. This circuit also provides means for automatically indexing the various parts to compensate for reduction in wheel size as the truing operation progresses.

In the operation of this machine the operator selects and mounts the desired wheel on the grinding wheel spindle and then selects the proper truing mechanism for the selected wheel by positioning the selector valve 65. The positionin of the selector valve plunger automatically positions a selector switch 9! which, as shown in Figure '7, is operatively connected to the selector valve plunger. The switch, which is shown in Figure 9, automatically conditions the electrical circuit for control of the proper truing mechanism, and interlocks the circuit in a manner to prevent operation of the other mechanism.

As shown in Figure 9, the switch 94 has an open position and a closed position. The open position corresponds to the position of the selector valve for eiiecting radius truing and corresponds to the position of parts in Figure 9. The efi'ect of this is that the relays CR9 and CR9A which are connected in series with the switch 94 by the line 95 between the power line 96 and the power line 9? remain deenergized whereby the normally open contacts CBS-3 and ORB-4 in lines 98 and 99 respectively remain open, and the normally closed contacts CRQ-I and CBS-2 in lines I88 and till remain closed. The normally closed contacts serve to connect the limit switches LS4 and LS5 associated with the truing diamond i8, Figure 10, to the control relays CR! and CR8, and the normally open contacts CBS-3 and CBS-4 serve to disconnect the limit switches LS6 and LS! associated with the diamond ll,

Figure 10, from the control relay CR! and CR8. These contacts provide an interlocking arrangement whereby only one set of limit switches can be connected at a time to the control relays.

Attention is invited to the relation. of the limit switches as shown in Figure 10. The position I82 of the diamond it constitutes the rest and starting position, and in this position the control dog 62, shown in Figure 3, rests against the limit switch LS5 and holds its contact LS5-l in a closed position. Similarly, the position I03 of diamond I! is its normal rest and starting position in which a control dog operatively connected with the slide il" holds the limit switch LSl-l in its closed position. It is also to be noted that under these conditions the reversing valve plunger I3 is in the position shown in Figure 7 with its solenoid 5 deenergized.

Considering now automatic cycle operation of the truing diamond t8, the operator energizes the circuit by pressing the start button which closes the circuit through line 185 to the control relay CR5. This relay closes its latching contact CRG-l, thereby permitting release of the starting button by the operator. The relay CR6 also closes a second switch CR6-2 in line 185 leading to the truing starting switch Illl. When the latter switch is closed, a circuit is completed to the line I00. Since limit switch L554 is held closed by its operating dog as just explained, and the contact LS4I of limit switch LS4 is a normally closed contact, the circuit is complete through line IIiIl to relay CR! and relay CRIA. The relay CR'I closes its contact GREY- in line I08 and completes a circuit to solenoid 5 which shifts the reversing valve plunger '53 shown in Figure '7 and thereby connects the pump to cylinder 69. This moves the piston 58 to the right as shown in Figure '7, and through the operative connection by means of the band 54 the piston 59 is moved to the left. This releases the limit switch LS5-I which opens, but the circuit has been latchedin by the closing of contact CRY-i by relay CR1.

When the diamond completes a pass in one direction, the limit switch LSA-I is operated,

opening its normal closed contact, thereby releasing the relay CR1, which opens contact CRl-S to solenoid 5, causing shifting of the reversing valve.

The hydraulic circuit then functions to return the truing diamond and as it starts back it releases limit switch LS4-E which assumes its normally closed position but since the latching contact CRL! is open, due to the release of relay CR1, a circuit is not reestablished until completion of the return movement when LS5 is again closed.

The cyclic operation of the other truing diamond is effected by similar mechanism after the operator has made the selection by closing switch 94. This causes actuation of control relay CR9 which opens contacts CR9! and CBS-2, and closes contacts CBS-3 and CBS-4. This connects the limit switches LS6 and LS7 to relay CR? and disconnects limit switches LS4 and LS5. The

limit switch LSI-I is held closed by a trip oleclosing of switch CRl-E in line ItB. As the truing diamond completes its pass it opens limit switch LSG-I, which thereby breaks the circuit to control relay CR1, opening its latch contact CRI-Z and opening the circuit to solenoid 5. The

reversing valve returns to its original position I and the hydraulic circuit retracts the truing diamond, closing limit switch LSfi-I but this does not affect the relay CRl'because of the opening of its latching contact CRT-2. The return movement continues until a trip element closes limit switch L314, and the circuit is in condition to repeat the cycle.

The requirements of this machine are such which is closed during the first cycle by either limit switch LS4-2 through switch CRB-Z or by limit switch LSB-Z through switch CBS-4. Regardless of which switch energizes the relay CR8 itis latched in by its contact CRB-I or CR8-2 so that. a circuit is completed from line I06 through line I39, to line III and relay CR8, and this relay will remain closed for the remainder of the two cycles or until the switch ORG-2 is opened. Line 2 has serial switches CR'IA-I and CR8-3 leading to relay CRIO. This line H2 is directly connected to line I06. It will be noted that the relay CR8 is energized midway of the first cycle of operation of either diamond by either limit switch LS4-2 or LSB-Z, and in so doing the relay closes the latching contacts CR8% and CRB-Z whereby the relay remains energized after these switches are open on the return movement of the first cycle. Although the relay CR8 closes the contact CR8-3 in line I I2 it did so at the same time that relay CR'IA is deenergized so that the circuit to relay CRIB is not completed until the end of the first cycle of truing which results in the closing of switch CRIA-I, the relay CR'IA being operated simultaneously with the relay CR1.

The result is that at the end of the first truing or roughin cycle the relay CHI 8 is energized and closes its latching contact CRIB-I. The operation of relay CR8 alsol closes another of its contacts one-s which is in line II3 leading to relay CE! I. At the end of the first cycle, another contact CRiii-Z in line II 3 is closed by the relay CRlG but a third contact CR'lA-Z in the line H3 is opened by relay CRT-A at the end of the first cycle so that the circuit is not completed to relay CRII until the midpoint of the second cycle at which time CR'IA-Z closes and thereby completes the cycle to relay CRI I.

The function of relay CRI I is to automatically stop the cycle, and it has a normally closed contact CRI l-I in line 105, and it will be noted from the foregoing description that relay CRI I is energized at the midpoint in the second cycle at which time it will open its normally closed contact CRI I -I The circuit, however, to relay CR6 is maintained at this particular point by either the normally closed contact LS5-2 of limit switch LS5, or the normally closed contact LS'I-2 of limit switch LS1. ,At the midpoint of the cycle the limit switches LS5 and LS'I are released and are not trip operated again until the end of the sec- 0nd cycle. Therefore, with CRI i-l held open at that in truing the wheels it is satisfactory to M make a roughing cut across a wheel over and back and then without further adjustment of the diamond, make another pass over and back to effect a finish truin operation. In view of this, the control cycle is designed for this method of operation; in other words, two cycles in succession without adjustment of the diamond.

Means are provided for automatically stopping the patricular mechanism after completion of the two cycles and before any more truing is done. The indexing of the diamond may be effected automatically either at the end of a previous cycle or at the beginning of a new cycle before the actual traverse of the diamond. In this invention the indexing of the diamond and the compensation in the position of the work support is effected automatically at the end of the finish truing cycle so that the diamond is in proper position to take a roughing cut the next time that the circuit is operated. The indexing and compensation is initiated by the control relay CR8 the midpoint of the second cycle it is obvious that at the end of the second cycle either LS5-2fior LEV-2 will be opened, which results in denergization of the control relay CR6.

The indexing and compensation is initiated by control relay CRIZ. This relay is actuated immediately upon the closing of switch I01, which initiates the start of a truing operation by energizmg relay CR1. This relay immediately closes its contacts CRl-3 in line I I4 which is directly connected to relay CRIZ. The relay closes its latching contact CRIZ-l in line I I5 and in series with normally closed contact TRZ-I of a timer relay. Thus, at the very start of the truing operation the relay CRZZ is energized, and in so doing closes its contact CRI2-3 in line II'B', thereby energizing the rectifier II8 which, in turn, energizes all three of the magnetic clutches.

It should be remembered that this is merely energization of the clutches but does not cause any movement at the point. A relay CRI3 actually controls the actuation of the solenoids of the respective clutches, but the circuit is arranged in the following manner so that this relay is not operated until the truing operation is completed. In the line 6 leading to the relay CR|3 there is a contact CRI2-2 which is closed by the relay CRH and the normally closed contact TR3-| of a second timer relay TR3. Also, in this line is the normally closed contact CBS-3 of the starting control relay CR6, which is held energized throughout the truing operation, and therefore this contact is held open until the truing operation is automatically stopped, at which time this contact will close and energize relay CRI3. This relay will close its latching contact CRI3-| which is shunted around the contact CR'Z-Z.

The contact CRT-4 in line I I7, shunted around the contact TR3-l, is closed at the end of the truing operation and is held closed so long as relay CR! is energized. The relay CRl3 closes a contact CRI3-2 in line H9 which leads to timer relays 'IRZ and TR3 connected in parallel to line H9. These timer relays are adjusted to effect a delayed closing, but the timing on relay TRZ is less than the timing on relay TR3. During this interval of time the relay CRl3 has closed one contact CRI3-3 in line I20 and another contact CRIS-4 in line "2 I. The line 120 is connected in parallel to solenoids 4 and AA by the selector switches CR9AI and CRBAJ. The contact CR9A-2 is a normally closed contact, while the other is normally open, and this condition corresponds to the open condition of selector switch 94, and when this switch is closed the condition is reversed in that CRBA-l is closed and CRHA-2 is opened.

Therefore, the closing of contact CRl3-3 selectively operates the magnetic clutch of the indexing mechanism of the truing diamond which has just been operated. At the same time the contact CRIB-s causes operation of the solenoid and thereby effects a compensatory movement of the work support.

After these movements have been completed the timer relay TR2 operates to open contact TR2-I in line H5, thereby deenergizing control relay CR! 2. The relay CRIZ then opens its contact CRI22 in line H 6, but the circuit is maintained by the latching contact CRI3-l until the timer relay contact TEE-i is opened by the later operation of timer relay TR3. By this arrangement the prior operation of relay CRIZ opened contact CRI2-3 in line I thereby deenergizing the magnetic clutches, and then the subsequent operation of relay CRI3 denergizes the operating solenoids for the clutches, permitting return of the operating arms by the mechanica1 means previously described. It is desirable that there be a momentary delay to permit the residual magnetism in the clutches to leak away before the solenoids are deenergized and thereby insure against any retrograde movement when the operating arms are returned.

There has thus been provided an improved mechanism for selective truing of alternatively mountable grinding wheels of difierent profile on a grinding machine utilizing substantially the same hydraulic actuating mechanism and an accompanying control circuit which is selective to control the truing operation of either grinding wheel.

What is claimed is:

1. In a grinding machine having a support, a grinding wheel spindle housing mounted on said support, and a spindle journaled in said housing adapted to receive interchangeable grinding wheels of different profiles, the combination of separate mechanisms mounted on the housing for truing the respective wheels including separate power operable means connected to each mechanism, a common actuating. and control mechanism for said power operable means including a common reversing mechanism therefor, electrically operable means connected to said reversing mechanism including a control relay, separate trip operable means operatively associated with each truing mechanism, and selector means for selectively coupling the power operable means of one truing mechanism to said reversing mechanism and simultaneously coupling the trip operable means associated with said one truing mechanism to said control relay.

2. In a grinding machine having a support, a spindle housing mounted on said support, a grinding wheel spindle journaled in said housing for interchangeably receiving grinding wheels of dif ferent profiles, the combination of separate truing mechanisms mounted on said housing for truing the respective profiles of the different wheels, separate power operable means connected to each of said mechanisms, a common actuating and control circuit for said power operable means including a reversing valve, means to selectively connect said power operable means to said valve, electrical shifting means in said circuit connected to said reversing valve, separate trip operable means operatively associated with each of said power operable means, separate electrical means for indexing each of said mechanisms toward the spindle, and selector means for simultaneously connecting the trip operable means and the indexing means of a particular truing mechanism to said control circuit.

3. In a truing mechanism for a grinding machine having a spindle for receiving interchange able grinding wheels of different profiles, and a housing for supporting said spindle. the combination of means mounted on the housing for selectively truing said wheels including a first truing mechanism for producing one profile, a second truing mechanism for producing a second profile, separate fluid operable actuating means connected to the respective mechanisms, a source of fluid pressure, a reversing valve supplied by said source, a selector valve for connecting the fluid output from reversing valve to either of said fluid operable means in accordance with the profile of the wheel in situ, electrically operable shifting means connected to said reversing valve, separate trip operable control means operatively associated with the respective mechanisms, and means operable by said selector valve for operatively selectively connecting one trip control means to said electrical means for controlling the power shifting of said reversing valve.

4. In a truing mechanism for a grinding machine having a spindle for receiving interchangeable grinding wheels of different profiles and a housing for supporting said spindle, the combination of means mounted on the housing for selectively truing said wheels including a first truing mechanism for producing one profile, a second truing mechanism for producing a second profile, separate power operable means connected to the respective mechanisms, a source of power having a reversing means, a selector operable to couple the reversing means to either of said power operable means in accordance with the profile of the wheel in situ, power operable shifting means connected to said reversing means, separate trip control means mounted in operative relation to the 11' respective mechanisms, and individual connectors for the respective trip control means alternatively operable by the selector as it makes its selection of a particular truing mechanism to connect the trip control means associated therewith to said power operable shifting means.

5. In a grinding machine having a bed, a spindle housing mounted on the bed, and a grinding wheel spindle journaled in the housing and adapted to receive interchangeable grinding wheels, a work support guided on the bed for adjustment of work toward the grinding wheel spindle, the combination of separate truing mechanisms for the respective wheels mounted on the housing, each mechanism having a truing tool supported for adjustment radially of the wheel, separate power operabl means connected to each tool for effecting adjustment thereof, additional power operable adjusting means connected to said work support, a truing cycle control mechanism for the machine including a control switch, each of said power operable means for the tools having a circuit selectively connectable to said switch, additional circuit meanscoupling the work support adjusting means to said switch, and means operable by said switch for energizing the circuits connected thereto whereby one or said truing tools and the work support may be adjusted simultaneously toward the wheel.

' FREDERICK S. HAAS.

WINTHROP TRIBLE. 

